1. Field
The present disclosure relates to image sensors and, in particular, aspects of the present disclosure relate to color filter arrays for image sensors.
2. Discussion of Related Art
Image sensors are used to capture light in a way such that an electronic representation of an illuminated scene can be captured, manipulated, stored, and accessed. A typical image sensor can be fabricated using complementary metal oxide semiconductor (CMOS) technology. Charge couple device (CCD) technology is also suitable.
Conventional CMOS and CCD image sensors suffer from some limitations, however. Both CMOS and CCD images sensor have relatively poor sensitivity to blue light because blue light has a wavelength that is relatively short, and the photons are absorbed relatively close to the surface of the silicon that is used to form the image sensor. When the photons are absorbed close to the surface, there is typically recombination with surface states or recombination by holes due to the P+ surface of the image sensor. The recombination reduces the sensitivity of the sensor because the loss of free electrons reduces the amount of free electrons that are produced during integration (e.g., during an exposure time).
Furthermore, conventional image sensors use filters to capture photons of various wavelengths in different pixels. For example, red, green, and blue (RGB) filters are provided such that an image can be reproduced using an additive color scheme. Conventional image sensors often arrange each of the filters using a Bayer pattern. The pattern uses one red pixel, two green pixels in diagonally opposing corners, and one blue pixel (RGGB). Two green pixels are chosen because the human vision system is most responsive across the green portion of the visible light spectrum. However, using the filters in the RGGB format often results in images that have poor sensitivity to blue wavelengths of light and that have poor noise characteristics. The above problems are typically made especially worse in low light situations.